That is unusual - not impossible, but highly unusual in domestic ducks. Some wild ducks - that only lay in the spring - can lay 2 eggs in one day - but it is NOT common for duck - just like healthy chickens only lay one egg per day (unless one is 'backed up' and another starts being processed - so once the problem egg is laid, the other egg will be laid shortly thereafter - but only 1 is produced per day by a chicken.)My BIL Runners laid 2 eggs a day ? He said that was normal- ? I know nothing about ducks. Other than they are complete quacks.